1. Field of the Invention
The present invention relates to a high voltage semiconductor device having level shifters, and more particularly, to a high voltage semiconductor device in which lateral diffusion metal oxide semiconductor (LDMOS) transistors for level shift are electrically isolated from a high voltage unit, and a method of fabricating the same.
2. Description of the Related Art
High voltage integrated circuits (HVICs) in which at least one high voltage transistor and low voltage circuits are arranged on a single chip are widely used in power control systems such as switching power supplies and motor drivers. An HVIC includes a high voltage unit, a low voltage unit, and a junction termination between the high voltage unit and the low voltage unit. In the junction termination, which isolates the high voltage unit from the low voltage unit, level shifters, which level shift signals from the low voltage unit and supply the same to the high voltage unit, are arranged.
Lateral diffusion metal oxide semiconductor (LDMOS) transistors are used as the level shifter. A high break down voltage and a low on-resistance are required in the LDMOS transistor, and can be obtained by employing a reduced surface field (RESURF) technique.
However, noise such as a cross talk occurs between a high voltage unit and lateral diffusion metal oxide semiconductor (LDMOS) transistors, in a conventional high voltage semiconductor device in which the LDMOS transistors are arranged in a junction termination as level shifters since the high voltage unit is not electrically isolated from the LDMOS transistors.